The location of the active-site histidine residue in the primary sequence of papain.
Papain that had been irreversibly inhibited with 1,3-dibromo[2-(14)C]acetone was reduced with sodium borohydride and carboxymethylated with iodoacetic acid. After digestion with trypsin and alpha-chymotrypsin the radioactive peptides were purified chromatographically. Their amino acid composition indicated that cysteine-25 and histidine-106 were cross-linked. Since cysteine-25 is known to be the active-site cysteine residue, histidine-106 must be the active-site histidine residue.
D000096:Acetone; D000595:Amino Acid Sequence; D001665:Binding Sites; D001966:Bromine; D002247:Carbon Isotopes; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D002918:Chymotrypsin; D003545:Cysteine; D006639:Histidine; D008745:Methylation; D010206:Papain / Q000032:analysis / Q000037:antagonists & inhibitors; D010455:Peptides / Q000032:analysis; D010944:Plants / Q000201:enzymology*; D011492:Protein Hydrolysates; D014357:Trypsin
D002247:Carbon Isotopes; D010455:Peptides; D011492:Protein Hydrolysates; D000096:Acetone; D006639:Histidine; D002918:Chymotrypsin; D014357:Trypsin; D010206:Papain; D003545:Cysteine; D001966:Bromine